/*******************************************************************************
 * Copyright (c) 2014 IBM Corp.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Ian Craggs - initial API and implementation and/or initial
 *documentation
 *******************************************************************************/
#include <string.h>
#include "MQTTPacket.h"
#include "StackTrace.h"

#define min(a, b) ((a < b) ? a : b)

/**
 * Validates MQTT protocol name and version combinations
 * @param protocol the MQTT protocol name as an MQTTString
 * @param version the MQTT protocol version number, as in the connect packet
 * @return correct MQTT combination?  1 is true, 0 is false
 */
int MQTTPacket_checkVersion(MQTTString* protocol, int version) {
    int rc = 0;

    if (version == 3 && memcmp(protocol->lenstring.data, "MQIsdp",
                               min(6, protocol->lenstring.len)) == 0)
        rc = 1;
    else if (version == 4 && memcmp(protocol->lenstring.data, "MQTT",
                                    min(4, protocol->lenstring.len)) == 0)
        rc = 1;
    return rc;
}

/**
 * Deserializes the supplied (wire) buffer into connect data structure
 * @param data the connect data structure to be filled out
 * @param buf the raw buffer data, of the correct length determined by the
 * remaining length field
 * @param len the length in bytes of the data in the supplied buffer
 * @return error code.  1 is success, 0 is failure
 */
int MQTTDeserialize_connect(MQTTPacket_connectData* data,
                            unsigned char* buf,
                            int len) {
    MQTTHeader header = {0};
    MQTTConnectFlags flags = {0};
    unsigned char* curdata = buf;
    unsigned char* enddata = &buf[len];
    int rc = 0;
    MQTTString Protocol;
    int version;
    int mylen = 0;

    FUNC_ENTRY;
    header.byte = readChar(&curdata);
    if (header.bits.type != CONNECT)
        goto exit;

    curdata +=
        MQTTPacket_decodeBuf(curdata, &mylen); /* read remaining length */

    if (!readMQTTLenString(&Protocol, &curdata, enddata) ||
        enddata - curdata <
            0) /* do we have enough data to read the protocol version byte? */
        goto exit;

    version = (int)readChar(&curdata); /* Protocol version */
    /* If we don't recognize the protocol version, we don't parse the connect
     * packet on the basis that we don't know what the format will be.
     */
    if (MQTTPacket_checkVersion(&Protocol, version)) {
        flags.all = readChar(&curdata);
        data->cleansession = flags.bits.cleansession;
        data->keepAliveInterval = readInt(&curdata);
        if (!readMQTTLenString(&data->clientID, &curdata, enddata))
            goto exit;
        data->willFlag = flags.bits.will;
        if (flags.bits.will) {
            data->will.qos = flags.bits.willQoS;
            data->will.retained = flags.bits.willRetain;
            if (!readMQTTLenString(&data->will.topicName, &curdata, enddata) ||
                !readMQTTLenString(&data->will.message, &curdata, enddata))
                goto exit;
        }
        if (flags.bits.username) {
            if (enddata - curdata < 3 ||
                !readMQTTLenString(&data->username, &curdata, enddata))
                goto exit; /* username flag set, but no username supplied -
                              invalid */
            if (flags.bits.password &&
                (enddata - curdata < 3 ||
                 !readMQTTLenString(&data->password, &curdata, enddata)))
                goto exit; /* password flag set, but no password supplied -
                              invalid */
        } else if (flags.bits.password)
            goto exit; /* password flag set without username - invalid */
        rc = 1;
    }
exit:
    FUNC_EXIT_RC(rc);
    return rc;
}

/**
 * Serializes the connack packet into the supplied buffer.
 * @param buf the buffer into which the packet will be serialized
 * @param buflen the length in bytes of the supplied buffer
 * @param connack_rc the integer connack return code to be used
 * @param sessionPresent the MQTT 3.1.1 sessionPresent flag
 * @return serialized length, or error if 0
 */
int MQTTSerialize_connack(unsigned char* buf,
                          int buflen,
                          unsigned char connack_rc,
                          unsigned char sessionPresent) {
    MQTTHeader header = {0};
    int rc = 0;
    unsigned char* ptr = buf;
    MQTTConnackFlags flags = {0};

    FUNC_ENTRY;
    if (buflen < 2) {
        rc = MQTTPACKET_BUFFER_TOO_SHORT;
        goto exit;
    }
    header.byte = 0;
    header.bits.type = CONNACK;
    writeChar(&ptr, header.byte); /* write header */

    ptr += MQTTPacket_encode(ptr, 2); /* write remaining length */

    flags.all = 0;
    flags.bits.sessionpresent = sessionPresent;
    writeChar(&ptr, flags.all);
    writeChar(&ptr, connack_rc);

    rc = ptr - buf;
exit:
    FUNC_EXIT_RC(rc);
    return rc;
}
